1. Department of Pediatric Oncology, Hematology and Clinical Immunology Heinrich Heine University Düsseldorf Düsseldorf Germany
2. Department of Pediatric Hematology and Oncology University of Freiburg Freiburg Germany
3. Department of Pediatrics and Adolescent Medicine University Medical Center Hamburg‐Eppendorf Hamburg Germany
4. Department of Pediatric Hematology and Oncology University Medical Center Hamburg‐Eppendorf Hamburg Germany